Because of documented contamination of about 50 square kilometers of land with putonium in the vicinity of the Rocky Flats nuclear weapons plant, there is community concern regarding possible health effects for populations living in this area as well as concern for the safety of further residential depelopment near the plant. A preliminary study of age-corrected death rates from leukemia in eight census tracts around the plant and in the city of Golden (a small city near Rocky Flats) compared with a control area consisting of 19 census tracts with a similar population in the relatively uncontaminated part of the county disclosed a significant increase in deaths from leukemia in the contaminated areas. An evaluation of age-specific death rates (45-64 years) for each of the contaminated areas compared with the control area disclosed a death rate from lung cancer more than twice as great as that for the control area. I propose to expand the study by evaluating death rates and incidence rates of leukemia, lung cancer, and other types of tumors in these and other study areas in the Denver metropolitan area, by census tracts. Study areas will be selected by known levels of plutonium in surface respirable dust and for inventory levels. This phase of the study will continue through the census year 1980, and will be completed by the end of the calendar year 1981. Cancer death and incidence data will be supplied by the Colorado Health Department, Division of Vital Statistics. The effects of exposure to low levels of plutonium on a general population living in a contaminated area has never yet been evaluated with this epidemiological approach, and the results will be of considerable value in selecting sites for plutonium processing plants and nuclear electric generating plants in relation to population centers. This study will be followed by a prospective study extending to 1991.